The index closed 11.94 points lower after gaining 3.72 points in the previous session.
Trading on the Ho Chi Minh Stock Exchange increased by 28% to VND18.878 trillion (US$743.7 million).
The VN-30 basket, comprising the 30 largest capped stocks, saw 16 tickers closed in the red.
HPG of steelmaker Hoa Phat Group saw the biggest drop of 4.7%, followed by FPT of IT giant FPT Corporation with a 2.8% decline and MWG of electronics retail chain Mobile World, down 2.5%.
Nine blue chips gained. STB of Ho Chi Minh City-based lender Sacombank went up 2.7%.
MSN of conglomerate Masan Group rose 1.6% and BVH of insurance company Bao Viet Holdings closed 1.5% higher.
Foreign investors were net seller to the tune of VND442 billion, mainly selling FPT and HPG.
The HNX-Index for stocks on the Hanoi Stock Exchange, home to mid and small caps, fell 0.66%, while the UPCoM-Index for the Unlisted Public Companies Market went down 0.62%.